Axial flow fan



Dec. 6, 1966 J. 1. R. BOIVIE AXIAL FLOW FAN Filed June 21, 1965 901m WM M ATTORNEY W mg 6?! W United States Patent 3,289,920 AXIAL FLGW FAN Jean Ivan Ragnar Boivie, Stockholm, Sweden, assignor to Aktiebolaget Electrolux, Stockholm, Sweden, 21 corporation of Sweden Filed June 21, 1965, Ser. No. 465,310

Claims priority, application Sweden, June 23, 1964,

11 Claims. (Cl. 230-117) My invention relates to axial flow fans.

An object of my invention is to provide an improved axial flow fan of simplified construction.

Another object of my invention is to provide an improved axial flow fan constructed in such manner that a fan of given overall size driven by an electric motor of appropriate capacity will deliver "an optimum quantity of air.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In the drawing FIG. 1 is a perspective view of an axial flow fan embodying my invention, some of the parts within the fan being illustrated by dotted lines; and FIG. 2 is a vertical sectional VlB'W- of the fan illustrated in FIG. 1.

Referring to the drawing, an axial flow fan which I have shown embodying my invention includes a casing 11 formed with top and bottom air inlet and outlet openings 12 and 14, respectively. The casing 11 comprises a main body section 11a of cylindrical form which extends upward from the outlet 14 and may be referred to as a bottom casing section, a neck portion 11b which extends downward from the air inlet 12 and may be referred to as a top casing section, and an intermediate section 110 which is disposed between the top and bottom casing sections 11a and 11b and flares radially outward from the axis of the casing 11 and also extends axially thereof.

The intermediate casing section 110 extends from the top casing section or neck portion 11b of one diameter to the bottom casing section or main body portion 11a of larger diameter. Essentially, the intermediate casing section 110 is of conical form with its inner surface facing downward toward the air outlet 14.

An electric motor 15 is supported concentrically within the casing 11 in any suitable manner, as by circumferenti'ally spaced supports 16, for example, having their inner and outer ends respectively fixed to the motor 15 and casing 11. The motor 15 is provided with a shaft 17 which extends upward therefrom and to which is secured a fan 13 having a plurality of blades 18a extending radially outward from the motor shaft 17 toward the neck portion 11b of the casing 11. The top parts of the fan blades 18a are disposed within the neck portion 11b of the casing 11 at the vicinity of the air inlet 12, and the extreme outer edges of the blades are spaced from the neck portion 11b to provide gaps 19 thereb'etween.

As best shown in FIG. 1, the fan blades 18a are fixed to the shaft 17 with their inner ends tangential to the peripheral surface of the shaft. Further, the axially disposed blades 18a extend vertically downward from the neck portion 1112 into the interior 20 of the casing 11. The bottom edges of the fan blades 18a are curved and conform to the shape of the top convex side of a dished member or plate 21 of circular form, the bottom concave side of which faces the air outlet 14. The bottom edges of the blades 18a are fixed to the top convex side of the dished member 21, the peripheral edges of "ice the blades terminating at the periphery of the plate 21 and extending substantially p'arallel'to the axis of the casing 11.

An apertured plate 22 of circular form isv provided within the bottom casing section 11a at the vicinity of the air outlet 14. The plate 22 is formed witha central opening 22a of circular form into which the bottom of the electric motor 15 extends, the diameter of the opening 22a being sufficiently large toprovide a gap 23 between the motor and the inner peripheral edge of the plate 22. Hence, the inner diameter of the apertured plate 22 is slightly greater than that of the electric motor 15.

Further, the outer diameter of the apertured'plate 22 is less than the diameter of the bottom casing section to provide a gap 24 therebetween. Y The apertured plate 22 is supported within the casing 11 by'a plurality of radially disposed supporting members or guide bars 25, the outer ends of which are fixed at 26 to the' bottom casing section 11a and the inner ends of which terminate at regions 27 at the underside of theplate 22 adjacent to and removed from the central opening 22athere in;

In the embodiment of;theinv'entio'ri beiiig'described and illustrated, the fan 10 is employed .to cause air to flow past a' heat exchange unit "23 of cylindrical form having a flange 28a adapted to be fixed in any's uitable manner (not shown) to a flange 114 formed at-th lowor end of the bottom-casing section 11a. The heat exchange unit 28 includes piping 29 to which heat transfer fins So are fixed and through which a coolingor heating medium is circulated to promote cooling orheating, respectively, of the air moved past the piping 29 and the fins 3a). The heat exchange unit 28 is provided with inlet and outlet connect-ions 31 and 32 for respectively in troducing and discharging the cooling or heating medi um to and from the piping 29. j I

In the operation of my improved axial flow fan 10, air is drawn into the air inlet 12 by the rotatable fan blades 18a. The air flows through the casing 11 in the manner diagrammatically shown by the dotted lines A in FIG. 1 which are arrowed to indicate downward flow of air from the inlet 12 to the outlet 14. The fan'blades 18a propel the air downward through the neck portion or top casing section 11b of the casing 11. A part of the kinetic energy developed in the air stream produced by air flowing through the neck portion 11b is changed to potential energy in the conical casing section 110 and bottom casing section 11a, such change in the form of energy of the moving air stream being due to the air moving from the top casing section 11b of one diameter to the bottom casing section 11a of larger diameter.

A rotational or swirling motion is imparted to the air stream in that part of its path of flow along the conical casing section 110 and the bottom casing section 11a to an intermediate region thereof at which the gap 24 is formed between the periphery of the plate 22 and the upright wall of the bottom casing section 11a. The rotational or swirling motion of the air stream stops at the gap 24. The air passes through the gap 24 between the members 25 and then flows axially from the plate 22 to the outlet 14. From the outlet 14, the axially flowing air passes in heat exchange relation with the piping 29 and fins 30 of the heat exchange unit 28, as explained above.

A small part of the air flowing downward in the bottom casing section 11a flows through the gap 23 between the motor 15 and inner periphery of the apertured plate 22. In this way some of the air is effectively utilized to promote cooling of the electric motor 15.

The axial length of the fan blades 18a can vary within a relatively wide range. As shown in FIG. 2, the fan blades 18a extend axially downward a substantial distance from the lower end of the top casing section or neck portionllb and terminate at a level below the top end of the bottom casing section 11a. The axial length of the fan blades 18a may be decreased, if desired, so that the bottom edges-of the fan blades 18a at their extreme outermost portions are at the same level as the juncture of the neck portion 11b and the conical casing section 110. Irrespective of the level of the bottom peripheral edges of the fan blades 18a with respect to the top end of the conical casing section 110, the sloping wall defining the intermediate conical casing section is substantially parallel to the downward sloping radially extending wall defined by the dished member 21.

As explained above, the members 25 function to support the apertured plate 22 within the casing 11. Further, the members 25, which are essentially fiat and the flat sides of which extend axially of the casing, function as guide bars or vanes to stop the rotational or swirling movement of the air stream at the gap 24 and promote axial flow'of air within the bottom casing section 11a to the outlet 14.

Instead of fixing the outer ends of the members 25 directlyto the bottom casing section 11a at 26, as explained above, the bottom edges of the members 25 may be fixed to the flanges 28a, of the heat exchange unit 28 in any suitable manner, such as by welding or brazing, for example.

The improved air flow fan described above and shown in the drawing provides a fan having components which are arranged in a compactmanner to provide a fan construction which is relatively quiet during operation. Moreover, a simple fabricated construction is obtained in which relatively close tolerances, such as the gaps 19 between the fan blades 18a and the top casing section 11b, for example, are avoided, so that precision assembly of the fan components is unnecessary. This produces an inexpensive and easily manufactured construction. Further, I have found that the particular relationship of the fan components provides a construction whereby a fan of given overall size driven by an electric motor of appropriate capacity will deliver an optimum quantity of air.

Although I have shown a single embodiment of my improved axial flow fan, I do not desire my invention to be limited to the particular arrangement set forth, and I intend in the claims to cover all modifications which do not depart from the spirit and scope of my invention.

I claim:

1. An axial flow fan comprising (a) a casing having top and bottom air inlet and outlet openings, respectively, the casing including a bottom casing section extending upward from the outlet and a top casing section extending downward from the inlet and in intermediate casing section therebetween having a downward sloping wall which flares radially outward from the axis of the casing and extends axially thereof, the intermediate casing section extending outward from the top casing section which is of one diameter to the bottom casing section which is of larger diameter, the intermediate casing section being of conical form,

(b) an electric motor, means for supporting the motor within the casing, the motor having a rotatable shaft which extends upward therefrom,

(c) a fan fixed to the shaft, the fan comprising a plurality of circumferentially spaced blades extending outward from the shaft, at least the top parts of the blades being disposed in the top casing section with their outer peripheral edges spaced from the top casing section to provide gaps therebetween,

(d) a dished member having a top convex side facing the inlet and a bottom concave side facing the outlet, the bottom edges of the blades conforming to the shape of the top convex side of the dished member and being fixed thereto,

(e) the fan blades and dished member being vertically disposed with respect to the casing to draw air into the top casing section at the inlet and propel air from the top casing section through the intermediate and bottom casing sections,

(f) an apertured plate which is disposed in the casing and substantially perpendincular to its axis, means for mounting the apertured plate within the casing at a region intermediate the top and bottom ends of the bottom casing section, the apertured plate having a central opening into which the lower end of the motor extends,

(g) the diameter of the apertured plate being less than that of the bottom casing section to provide a gap of annular form between the outer peripheral edge of the plate and the wall of. the bottom casing section, and

(h) circumferentially spaced vanes which extend across the last-mentioned gap and function to guide air flow ing past the vanes, the vanes being formed to impart axial flow to air passing from the gap to the outlet.

2. Apparatus as set forth in claim-1 in which the downward sloping wall of the intermediatecasing section and the dished member, from its center toward its outer peripheral edge, are substantially parallel.

3. Apparatus as set forth in claim 1 in which the top edges of the blades are disposed within the top casing section at the vicinity of the air inlet.

4. Apparatus as set forth in claim 3 in which the peripheral edges of the blades are upright and extend 'vertically upward from the vertical edge of the dished memher.

5. Apparatus as set forth in claim 3 in which the bottom peripheral edges of the blades are at least at a level below the juncture of the top and intermediate casing sections.

6. Apparatus as set forth in claim 5 in which the bottom peripheral edges of the blades are disposed between the upper and lower ends of the bottom casing section.

7. Apparatus as set forth in claim 1 in which the means for mounting the apertured plate in the casing includes the vanes.

8. Apparatus as set forth in claim 7 in which the vanes comprise elongated elements which extend from regions closely adjacent to the wall of the bottom casing section to regions closely adjacent to the inner periphery of the plate defining the central opening therein.

9. Apparatus as set forth in claim 8 in which the elongated elements are disposed at the underside of the plate and project across the gap from the outer peripheral edge of the plate.

10. Apparatus as set forth in claim 1 in which the inner peripheral edge of the central opening in the plate and the motor have a gap therebetween.

11. Apparatus as set forth in claim 1 in which the gaps between the outer peripheral edges of the blades and the wall of the top casing section are substantial and elimi mate the necessity for mounting the motor and fan within the casing with close precision.

References Cited by the Examiner UNITED STATES PATENTS 1,932,231 10/1933 Schmidt 230-l17 2,284,141 5/1942 Funk 230117 ROBERT M. WALKER, Primary Examiner. 

1. AN AXIAL FLOW FAN COMPRISING (A) A CASING HAVING TOP AND BOTTOM AIR INLET AND OUTLET OPENINGS, RESPECTIVELY, THE CASING INCLUDING A BOTTOM CASING SECTION EXTENDING UPWARD FROM THE OUTLET AND A TOP CASING SECTION EXTENDING DOWNWARD FROM THE INLET AND IN INTERMEDIATE CASING SECTION THEREBETWEEN HAVING A DOWNWARD SLOPING WALL WHICH FLARES RADIALLY OUTWARD FROM THE AXIS OF THE CASING AND EXTENDS AXIALLY THEREOF, THE INTERMEDIATE CASING SECTION EXTENDING OUTWARD FROM THE TOP CASING SECTION WHICH IS OF ONE DIAMETER TO THE BOTTOM CASING SECTION WHICH IS OF LARGER DIAMETER, THE INTERMEDIATE CASING SECTION BEING OF CONICAL FORM (B) AN ELECTRIC MOTOR, MEANS FOR SUPPORTING THE MOTOR WITHIN THE CASING, THE MOTOR HAVING A ROTATABLE SHAFT WHICH EXTENDS UPWARD THEREFROM, (C) A FAN FIXED TO THE SHAFT, THE FAN COMPRISING A PLURALITY OF CIRCUMFERENTIALLY SPACED BLADES EXTENDING OUTWARD FROM THE SHAFT, AT LEAST THE TOP PARTS OF THE BLADES BEING DISPOSED IN THE TOP CASING SECTION WITH THEIR OUTER PERIPHERAL EDGES SPACED FROM THE TOP CASING SECTION TO PROVIDE GAPS THEREBETWEEN, (D) A DISHED MEMBER HAVING A TOP CONVEX SIDE FACING THE INLET AND A BOTTOM CONCAVE SIDE FACING THE OUTLET, THE BOTTOM EDGES OF THE BLADES CONFORMING TO THE SHAPE OF THE TOP CONVEX SIDE OF THE DISHED MEMBER AND BEING FIXED THERETO, (E) THE FAN BLADES AND DISHED MEMBER BEING VERTICALLY DISPOSED WITH RESPECT TO THE CASING TO DRAW AIR INTO THE TOP CASING SECTION AT THE INLET AND PROPEL AIR FROM THE TOP CASING SECTION THROUGH THE INTERMEDIATE AND BOTTOM CASING SECTIONS, (F) AN APERTURED PLATE WHICH IS DISPOSED IN THE CASING AND SUBSTANTIALLY PERPENDICULAR TO ITS AXIS, MEANS FOR MOUNTING THE APERTURED PLATE WITHIN THE CASING AT A REGION INTERMEDIATE THE TOP AND BOTTOM ENDS OF BOTTOM CASING SECTIONS, THE APERTURED PLATE HAVING A CENTRAL OPENING INTO WHICH THE LOWER END OF THE MOTOR EXTENDS, (G) THE DIAMETER OF THE APERTURED PLATE BEING LESS THAN THAT OF THE BOTTOM CASING SECTION TO PROVIDE A GAP OF ANNULAR FORM BETWEEN THE OUTER PERIPHERAL EDGE OF THE PLATE AND THE WALL OF THE BOTTOM CASING SECTION, AND (H) CIRCUMFERENTIALLY SPACED VANES WHICH EXTEND ACROSS THE LAST-MENTIONED GAP AND FUNCTION TO GUIDE AIR FLOWING PAST THE VANES, THE VANES BEING FORMED TO IMPART AXIAL FLOW TO AIR PASSING FROM THE GAP TO THE OUTLET. 